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Yu Jianchun gives a lecture about his mathematical discoveries at the department of mathematics in Zhejiang University.(Photo from Weibo)

Yu Jianchun, an ordinary worker of a logistic company in Hangzhou, a city in east China's Zhejiang province gave a lecture about his mathematical discoveries at the department of mathematics in Zhejiang University recently.

33-year-old Yu is only a vocational school graduate. However, he is very interested in mathematics and research regarding mathematical problems in his spare time. It never occurred to him that one day he would stand on the podium of a university and his findings would be recognized by math professors. He explained to and discussed with professors and doctoral students about his five mathematical discoveries. From 10 a.m. to 12 a.m., Yu didn't take a single glance at his notebook or any reference materials, because "the numbers and equations are in my brain", as Yu said. 

After the lecture, the audience all thought that Yu's ideas were innovative and inspiring. Cai Tianxin, a math professor of the Zhejiang University, said that the most valuable finding of Yu is his criterion for the Carmichael number. Professor Cai has tested Yu’s equation and believed that in a certain scope, Yu's theory can help finding more Carmichael numbers with better efficiency. 

Because the process of argumentation of Yu's theory is not formal enough to be published as an academic paper, Professor Cai decided to include Yu's equation into his new work. He also gave a math book to Yu to encourage him to continue studying. 

Yu said that he got the opportunity to give the lecture because he sent a hand-written letter to Professor Cai this May. And it was also the first time that an expert had responded to him.